LTC1688 Linear Technology, LTC1688 Datasheet

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LTC1688

Manufacturer Part Number
LTC1688
Description
100Mbps RS485 Hot Swapable Quad Drivers
Manufacturer
Linear Technology
Datasheet

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FEATURES
APPLICATIO S
TYPICAL APPLICATIO
Ultrahigh Speed: 100Mbps
Guaranteed Propagation Delay: 8ns 4ns
Over Temperature
50Mbps Operation with V
Low Channel-to-Channel Skew: 500ps Typ
Low t
Hot Swap
Driver Outputs Maintain High Impedance in
Three-State or with Power Off
Short-Circuit Protected: 3mA Typ Output Current
for an Indefinite Short
Thermal Shutdown Protected
Single 5V or 3V Supply
Pin Compatible with LTC486/LTC487
High Speed RS485 Twisted-Pair Drivers
High Speed Backplane Drivers
Complementary Clock Drivers
STS-1/OC-1 Data Drivers
SCSI Drivers
1/4 LTC1688
DRIVER
PLH
/t
TM
PHL
Capable
Skew: 500ps Typ
100
U
50Mbps RS485 Data Connection
100 FT CATEGORY 5 UTP
DD
= 3V
U
100
RECEIVER
1/4 LTC1518
DESCRIPTIO
The LTC
bus/line drivers that can operate at data rates up to
100Mbps. Propagation delay is guaranteed at 8ns 4ns
over the full operating temperature range. These devices
operate over the full RS485 common mode range (– 7V
to 12V), and also meet RS422 requirements.
The driver outputs are Hot Swap capable, maintaining
backplane data integrity during board insertion and
removal. The drivers feature three-state outputs, maintain-
ing high impedance over the entire common mode range
(– 7V to 12V). Outputs also remain high impedance during
power-up and with the power off. A short-circuit feature
detects bus contention and substantially reduces driver
output current. Thermal shutdown circuitry protects the
parts from excessive power dissipation.
The LTC1688 allows all four drivers to be enabled together,
while the LTC1689 allows two drivers at a time to be
enabled.
The LTC1688/LTC1689 operate from a single 5V or 3V
supply and draw only 9mA of supply current.
Hot Swap is a trademark of Linear Technology Corporation.
1688/89 TA01
, LTC and LT are registered trademarks of Linear Technology Corporation.
Hot Swapable Quad Drivers
®
1688/LTC1689 are ultrahigh speed, differential
2V/DIV
2V/DIV
2V/DIV
5V/DIV
U
20ns Pulse Across 100 Feet
LTC1688/LTC1689
100Mbps RS485
of Category 5 UTP
CABLE DELAY
RECEIVER OUTPUT
DRIVER OUTPUTS
RECEIVER INPUT
DRIVER INPUT
20ns/DIV
1688/89 TA02
1

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LTC1688 Summary of contents

Page 1

... Thermal shutdown circuitry protects the parts from excessive power dissipation. The LTC1688 allows all four drivers to be enabled together, while the LTC1689 allows two drivers at a time to be enabled. The LTC1688/LTC1689 operate from a single supply and draw only 9mA of supply current ...

Page 2

... OUT OUT (RS422 (RS485), Figure Figure Figure ORDER PART TOP VIEW NUMBER DI4 LTC1688CS 3 14 DO4A LTC1689CS 4 13 DO4B 5 12 ENB (EN34 DO3B 7 10 DO3A 8 9 DI3 S PACKAGE ...

Page 3

... S1 Closed, Figures 15pF, S2 Closed, Figures (Note 3) (Note 3) Note 2: All currents into the device pins are positive; all currents out of the device pins are negative. Note 3: Guaranteed by design or correlation, but not tested. LTC1688/LTC1689 MIN TYP MAX 0.1 1.4 0 200 ...

Page 4

... LTC1688/LTC1689 W U TYPICAL PERFORMANCE CHARACTERISTICS Propagation Delay vs Temperature DIFF C = 25pF TEMPERATURE ( C) Supply Current vs Data Rate 250 200 4 DRIVERS SWITCHING 150 PER DRIVER DIFF C = 25pF, PER DRIVER L 100 ...

Page 5

... DI3 (Pin 9): Driver 3 Input. Do not float. DO3A (Pin 10): Driver 3 Noninverting Output. DO3B (Pin 11): Driver 3 Inverting Output. ENB (Pin 12, LTC1688): Low True Enable Pin, enables all four drivers. A low on Pin 4 and a high on Pin 12 will put all driver outputs into a high impedance state. See Function Tables for details ...

Page 6

... The LTC1688/LTC1689 have an ESD rating of 6kV human body model. 50Mbps with 3V Operation The LTC1688/LTC1689 are designed to operate with a 3V power supply and still achieve 50Mbps operation (see Electrical Characteristics table for 3V DC and AC specifica 1MHz ...

Page 7

... For cables with the recommended RS485 termination (no DC bias on the cable, see Figure 8), the LTC1688/LTC1689 will automatically come out of short-circuit mode once the physical short has been removed. ...

Page 8

... INFORMATION Cable Termination The recommended cable termination for use with the LTC1688/LTC1689 is a single resistor across the two ends of a transmission cable (see Figure 8). When PC traces are used as the transmission line, its characteristic imped- ance should be chosen close to 100 in order to better match the specified timing characteristics of the LTC1688/ LTC1689 ...

Page 9

... Figure 11. 8ns Pulse Over 25 Feet Category 5 UTP W U High Speed Backplane Transmission The LTC1688/LTC1689 can be used in backplane point-to- point and multipoint applications. At high data rates, signals should be routed differentially and PC traces should be terminated (see Figure 13). Note that the RS485 specification calls for characteristic impedances near 100 ; ...

Page 10

... The LTC1688/LTC1689 RS485 drivers and LTC1518/LTC1519 52Mbps RS485 receivers are the fast- est in the industry. The LTC1688/LTC1689 drivers can reach speeds over 100Mbps, with a rise and fall time of just 2ns. At speeds in excess of 52Mbps, the non-RS485 Lucent Technologies’ ...

Page 11

... RECEIVER OUTPUT 1688/89 F20 Figure 21. 200 Feet, 33Mbps, LTC1518 Receiver DRIVER INPUT RECEIVER INPUT 2V/DIV RECEIVER OUTPUT 1688/89 F22 Figure 23. 25 Feet, 100Mbps, BRF2A Receiver LTC1688/LTC1689 DRIVER INPUT RECEIVER INPUT RECEIVER OUTPUT 1 s/DIV 1688/89 F19 DRIVER INPUT CABLE DELAY RECEIVER INPUT ...

Page 12

... LTC1688/LTC1689 PACKAGE DESCRIPTION 0.010 – 0.020 45 (0.254 – 0.508) 0.008 – 0.010 0 – 8 TYP (0.203 – 0.254) 0.016 – 0.050 (0.406 – 1.270) * DIMENSION DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" ...

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